After 1,000,000 cycles of compressive cyclic loading, PMZ composite molar crowns were more fatigue-resistant than VMII ceramic crowns. Cement type had a significant effect on fatigue resistance of the ceramic crowns but not the composite ones. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other subgroups (p < 0.05).

Objectives To evaluate the wear resistance and abrasiveness of monolithic CAD/CAM ceramics. Materials and methods Rectangular-shaped specimens (12 mm × 6.5 mm × 1.5 mm) were sectioned from the following CAD/CAM blocks (n = 10); partially crystallized lithium disilicate (PLD), experimental fully crystallized lithium disilicate (FLD), zirconia-reinforced lithium silicate (ZLS), super-translucent monolithic zirconia (SMZ), and ultra-translucent monolithic zirconia (UMZ). Silicon carbide papers were used to mechanically flatten and polish the surfaces. PLD specimens were subjected to a combined crystallization/glazing firing cycle. Ceramic specimens were mounted to the wear device and tested for 200,000 cycles against human premolars at 20 N force and 2 mm sliding distance. Artificial saliva was used as a lubricant. The teeth were scanned using micro-CT before and after the wear test and the generated models were overlapped to determine the volumetric tooth loss. Before and after the test, specimens’ weights and surface roughness (Ra) values were measured, and the differences were calculated. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were utilized for microstructural and chemical analysis. Statistical analysis was performed using one-way ANOVA or an equivalent test for non-parametric results. Significance level was set at P ≤ 0.05. Results The type of ceramic material affected the ceramic and antagonist wear rates (P < 0.001). PLD and ZLS had the highest ceramic and antagonist wear, whereas UMZ and SMZ demonstrated the lowest wear values. The FLD group showed comparable antagonist wear and significantly less ceramic wear than PLD and ZLS. Conclusions Monolithic zirconia demonstrated the best wear resistance and least abrasiveness to the antagonist. The experimental lithium disilicate was more wear-resistant than other glass–ceramic groups. Clinical relevance Monolithic zirconia is wear-resistant and gentle on the antagonist. In contrast, glass–ceramics are more abrasive to enamel.

The resin cements are responsible to retention of the indirect materials decreasing marginal leakage, increasing failure resistance compared with conventional cementation. The cementation within root canal is very hard due unfavorable conditions regarding the application of adhesive techniques caused by inadequate access. Therefore, considering the possibility to decrease steps of cementation, this study was performed to evaluate the bond strength of self-adhesive resin cement (RelyX TM U100, 3M ESPE) and resin cement combined with self-ecthing adhesive system (Panavia ® F 2.0, Kuraray) light-cured with Quartz Tungsten Halogen (QTH) following storage at 37 °C immediately after light-curing, 24 and 48 hours and 7 days. The root canals were prepared to receive the glass fiber post in the depth of 10 mm, irrigated with 17% EDTA and NaOCl, rinsed with distilled water and dried using paper points. The roots were perpendicularly sectioned into approximately 1 mm thick sections, obtaining ninety-six slices (n = 12). The slices were trimmed using a cylindrical diamond bur in the proximal surfaces until it touched the post and attached into a device, which were mounted on a strength tester (Bisco) and loaded in tension at a speed of 0.5 mm/min until failure occurred at specimens. The analysis of variance (ANOVA) and Tukey's post-hoc tests showed significant statistical differences (P < .05) to all resin cements immediately after light-curing and 24 hours, 48 hours and 7 days. The Panavia ® F 2.0 showed higher mean values than RelyX TM U100 for all storage times, however no different statistically significant was reported (P > .05). The resin cements 24 and 48 hours after light-curing were statistically similar among themselves (P > .05). The both resin cement showed similar bond strength into root canal on different storage times. The highest bond strength values of the resin cements were showed 7 days after curing.

Aim: To evaluate fracture strength and change in structure of three types of ceramic crowns after debonding with Er,Cr:YSGG laser. Materials & Methods: A maxillary premolar tooth was prepared to receive an all-ceramic crown then duplicated into thirty resin dies. Dies were scanned with Omnicam intraoral scanner, and thirty ceramic crowns were milled with Cerec MCXL milling machine. Crowns were divided into three main groups according to their material type (n=10); group A (E-Max CAD), group B (Vita Enamic) and group C (InCoris TZI). Crowns were bonded to their dies using TheraCem adhesive resin cement. Each group was subdivided into two subgroups (n=5); subgroup 1: crowns were not subjected to laser and subgroup 2: crowns were subjected to laser. Subgroups (A2, B2, and C2) were debonded using Er,Cr:YSGG laser irradiation then rebonded again. Crowns were loaded to fracture with the use of a universal testing machine at a crosshead speed of 1 mm/min. Six rectangular specimens were milled from the three materials blocks. One specimen from each material was subjected to laser irradiation then all specimens were scanned using x-ray diffraction. Data were analyzed by one way ANOVA and paired t-test. Results: There was a statistically significant difference in mean fracture resistance between subgroups of group A: A1 (770.19± 15.04 N) and A2 (725.10± 8.28 N) and subgroups of group B: B1 (519.45± 20.24 N) and B2 (337.01± 25.97 N). There was no significant statistical difference in mean fracture resistance between subgroups of group C: C2 (1747.38± 61.30 N) and C1 (1737.26± 28.58 N). Conclusions: Er,Cr:YSGG laser debonding had a significant effect on the fracture resistance of the rebonded E-max CAD and Vita Enamic crowns and a non-significant effect on the rebonded InCoris TZI crowns fracture resistance.